In a movie theater, the cueing and activation of many functions which relate to the overall movie presentation are synchronized with the passage through the projector of indicia or cues attached to certain points on the motion picture film. The functions to be controlled may involve changes within the theater or may provide control adjustments within the motion picture projector. As an example of events within the theater, the detection of these indicia or cues is generally used to control the level of theater lighting, the opening of the curtain at the beginning of the movie presentation, etc. In addition, cues are used to automatically select various sound systems, as for example use of normal sound or enhanced sound (e.g. Dolby sound) systems, the control of "change over" devices which switch from one projector to another, and the control of lens assemblies on the projector (e.g. automatic switching between a normal "flat" lens and a cinemascope lens). Modern automated theater facilities increasingly rely on such cues to change projector lenses and apertures, control screen format size and select sound formats, in order to provide a fully automated projection system in which the expense of projector operators or other manual intervention is eliminated.
To provide cueing capability, the prior art has used various indicia or cues placed at selected locations along the motion picture film strip and has devised various schemes for detecting these cues to automatically activate the desired events. Many different types of cues and cue detection systems have been developed and used over the years. As one example of an early cue system, notches permanently cut into the edge borders of the motion picture film were detected by various mechanical arrangements. However, the notches tended to weaken the film and caused it to rapidly wear with use. The detection of magnetic strips and/or paint applied along the motion picture film has also been used as the basis for prior art cue systems, but these systems have not found widespread acceptance.
The prior art has also utilized bar coded labels attached at predetermined positions of the motion picture film strip to activate a particular cueing function. However, the labels are opaque and of a size which interferes with at least one picture frame. In my copending parent application Ser. No. 07/462,610, this problem has been solved by providing a visibly transparent bar code label, wherein the bar code symbols are printed with a special infra red ink that is not visible under ordinary light, but readable with an infra red sensitive bar code scanner. However, notwithstanding this improvement, the use of bar code labels and associated scanners in a cue detection system suffers from being overly complicated and extremely expensive for the intended usage, often resulting in expensive repairs. Therefore, this approach has not found widespread commercial acceptance.
The most widely used cue system in today's theaters operates by detecting the presence of electrically conductive cue strips adhesively attached to the edge borders of the film. The most commonly used conductive cue strip is a length of aluminum foil backed with adhesive. The presence of the aluminum foil is detected when the conductive cue strip enters a cue detector mounted on the projector and spans the space between two spaced-apart rollers in the cue detector to complete an electrical circuit.
This type of prior art cue detector is described in my Application Ser. No. 241,582, now abandoned. As shown therein, the prior art cue system operates by providing a pair of contacts which are momentarily bridged by the passage of the conductive cue strip. The contacts are metallic rollers which are spaced apart on insulated shafts, and arranged so that the rollers contact the edge borders of the film to which the electrically conductive cue strip has been attached. When the cue strip bridges the gap between the rollers, an electrical circuit is completed which activates a predetermined control function.
The cue detector is mounted on the projector housing so that the film is intercepted prior to the take up reel or platter. To ensure good electrical contact and positive cue detection, this prior art cue detector must be precisely aligned to the film path, and a relatively constant force must be maintained between the film and the rollers.
A second type of prior art cue detector system utilizes a sequential advance programmer activated by detection of cues placed on predetermined portions of the film. A single proximity detector mounted along the film path detects the proximate passage of a cue. The system is sequentially advanced with each detection to activate a preprogrammed sequence of control functions.
A problem inherent in the design of prior art cue detector systems is their inability to accommodate the growing demand by movie theater operators for control of an ever increasing number of functions. It is apparent that the number of unique ways in which prior art cues may be positioned is rather limited. Although conductive cue strips of different lengths may be used to identify different control functions, the detection of different length cues requires the provision of precise timing circuits in the cue detector system, and leads to undesirable complexity and expense.